The establishment of bone cells in vitro that exhibit and maintain an osteoblastic phenotype has long been a goal of the cell biologist interested in bone metabolism in health and in disease. By utilizing a new technique, osteoblasts from a variety of species (human, bovine and ovine) have been utilized to study the biosynthesis of bone-specific, non-collagenous extracellular matrix proteins, and to examine their potential physiological role and possible alterations in disease states. These cells also serve as a source of mRNA and DNA for studies of non-collagenous, bone specific proteins at the genomic level. In addition, the culture of tissue from various portions of the tooth is being used to establish cell populations including odontoblasts in vitro to study the biosynthesis of proteins (including phosphophoryn) involved with the formation of this hard tissue.